Records on up to 760,000 Japanese imprisoned in Soviet labor camps after World War II have been found at a national archive in Moscow, casting new light on what is regarded as a major tragedy involving Japanese in the war's aftermath, government sources said.

Japan has estimated that about 560,000 people were taken prisoner and 53,000 of them died after being taken to Siberia and other places to engage in railway construction and other work to supplement the lack of labor in the Soviet Union after the war, but the latest findings could lead to a review of the figures.

Russia has largely agreed to provide the newly found documents to the Japanese government, and the documents will start arriving as early as this year, the sources said.

The Health, Labor and Welfare Ministry has already confirmed the names of about 20 new detainees in the documents after asking Moscow to look for names matching those of some 300 people who previously had no records in the Soviet Union but were presumed to have died in the labor camps, they said.

The documents are in the form of cards with about a dozen categories, including name, birthday and travel record of the prisoners. It also shows when they died and where they were buried, possibly opening a path for relatives of the dead and surviving prisoners, who are now around 85 years old on average, to visit the sites.

The documents were found in 757 boxes, each containing about 1,000 cards. Each card contains information on a single person, but there could be multiple cards on a single person, the sources said.

Moscow has been providing Japan with documents on detainees at Siberian labor camps since reaching an agreement in 1991, and records on about 41,000 people who died have been turned over to date.